Known technology for hoisting or lifting systems on vessels, e.g., drilling-, intervention- and service vessels used in the offshore market, include winch-based systems (e.g., so-called drawworks) with a multiple stringed block. These may be arranged in a single wire or multi-wire setup. An alternative solution is a cylinder lifting rig, such as the RamRig™ technology.
A conventional configuration with drawworks uses a drum which winds up a single hoisting wire with very high line speed due to the gearing factor in the travelling- and crown block system. An example of a possible arrangement is described in WO 2013/076207 A2. A further example of a winch-based hoisting system is described in WO 2014/209131 A1 where the winch-based hoisting system comprises a winch with a winch drum, an elongated hoisting member, and where the elongated hoisting member is accommodated in a single layer on the winch drum.
A cylinder lifting configuration may utilise cylinders pushing directly onto a yoke on which a number of sheaves are attached. The hoisting wire is attached to an anchor at one end and to a load at the other end. The lifting speed is 2:1 between the load and the cylinder movement. A set of parallel wires can be arranged to lift a common load. An example of a possible arrangement is described in WO 97/23705.
Other documents useful for understanding the field of technology of the present invention include WO 2014/140367, US 2005/0191165, U.S. Pat. Nos. 4,552,339, 4,341,373, WO 97/24507, WO 01/77000, and U.S. Pat. No. 3,606,854.
Such hoisting systems for vessels will commonly be required to operate under varying operational conditions according to the particular operation carried out, for example, drilling, well intervention, or subsea installation. This may range from having to carry out very heavy lifts, to carrying out lighter lifts but where a high lifting speed is required. This is a challenge for designers of such systems since trade-offs will often exist between the different operational functionality and performance that can be realised.